Walt Disney Co Chief Executive Bob Iger will step down as CEO in March 2015 after nearly a decade at the helm, setting in motion a succession plan for the largest U.S. media and entertainment company.

The company did not mention possible successors, but industry speculation has centered on Chief Financial Officer Jay Rasulo and the head of Disney's huge theme parks and resorts division, Tom Staggs.

Iger, 60, succeeded Michael Eisner as Disney's CEO in October 2005, which means his tenure as chief executive will be less than a decade long.

Eisner's reign at Disney, which ranks among the longest and most storied -- both for better and worse -- in CEO history, lasted 21 years, from 1984 until 2005.

Disney shares were down 1 percent at $31.70 in afternoon trade. The company has increased in value by more than a third since Iger began his term.

Disney -- which generates some $40 billion in annual revenue -- is now grappling with economic uncertainty, and the potential impact on its three largest divisions: media, consumer products and theme park resorts.

In August, the company posted better-than-expected quarterly results, but Wall Street analysts warned that low consumer spending may hurt in coming months.

It's wise for Disney's board to have a very clear succession plan, said Miller Tabak & Co analyst David Joyce.

Still, he said, Iger's plan to leave the CEO post is a little surprising given he's still a little young-ish CEO.

Speculation that Iger might have identified a successor picked up after Disney said that Staggs and Rasulo were swapping jobs.

Staggs, 49, was known as a favored executive and is considered a potential successor to Iger, but the former Wall Street analyst lacked operational experience. By putting Staggs in charge of Disney's all-important theme parks, analysts said, Iger may have been affirming Staggs as a strong internal candidate for the top job while giving the finance chief much-needed operating experience.

Iger will hold the positions of chairman and chief executive officer through March 31, 2015. After vacating the CEO role, he will continue to serve as executive chairman of Disney's board through June 30, 2016.